<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
   let arr = ['a','b','c'];
   console.log("1:","a" in arr);
   console.log("2:",arr.indexOf('a'));
   console.log("3:",arr.includes('a'));


   </script>
</body>
</html>